Apparatus and method for image rendering based on white point correction

Abstract

Systems, methods and apparatus, including computer programs encoded on computer storage media, of this disclosure allow for forming an image frame on a display device. In one aspect, a controller associated with a display device can be configured to correct for output white point shift due to variation, across separate color subfields of an image frame, in the respective number of subframes or the respective subframe weights. The controller can determine aggregate subframe weights for at least two color subfields and adjust at least one display parameter based on the determined aggregate subframe weights, to shift the output white point towards a white point of a target color gamut. The display parameter(s) can include a duty cycle of a color subfield, tristimulus coordinates of light used to illuminate a color subfield or gamut mapping function. The controller can display the image frame according to the adjusted display parameter(s).

What is claimed is: 
     
         1 . A controller configured to:
 receive first image data for a first image frame;   generate, for each of a plurality of component colors, a respective number of first subframes based on the first image data, wherein at least two component colors are associated with different respective numbers of first subframes, such that the generated first subframes are associated with a first output white point;   cause the generated first subframes to be displayed;   receive second image data for a second image frame;   determine, for each of the plurality of component colors, a respective number of second subframes, for at least one component color of the plurality of component colors, the respective number of second subframes is different than the respective number of first subframes for that component color;   generate the second subframes based on the second image data, such that a second output white point associated with the second image frame is substantially the same as the first output white point; and   cause the generated second subframes to be displayed.   
     
     
         2 . The controller of  claim 1 , wherein for the generated second subframes, the plurality of component colors are associated with substantially equal respective duty cycles. 
     
     
         3 . The controller of  claim 1 , wherein for the generated second subframes, the plurality of component colors are associated with substantially equal respective cumulative luminances. 
     
     
         4 . The controller of  claim 1 , wherein generating the second subframes includes:
 determining subframe weights for second subframes associated with each of the component colors, such that a first aggregate weight associated with a first component color is different than a second aggregate weight associated with a second component color;   adjusting at least one display parameter used to output the second image frame based on the first and second aggregate weights, such that the second output white point is shifted towards the first output white point; and   generating the second subframes according to the identified numbers of subframes and the identified subframe weights.   
     
     
         5 . The controller of  claim 4 , wherein the at least one display parameter includes a duty cycle of the first component color. 
     
     
         6 . The controller of  claim 5 , wherein adjusting the duty cycle of the first component color includes:
 determining a cumulative duty cycle for the first component color based on the first aggregate weight;   determining a target cumulative duty cycle based on the first and second aggregate weights;   computing a scaling factor for the first component color based on the cumulative duty cycle for the first component color and the target cumulative duty cycle; and   determining display periods for second subframes associated with the first component color using the scaling factor.   
     
     
         7 . The controller of  claim 4 , wherein the at least one display parameter includes at least a chromaticity or luminance of light used to illuminate the first component color. 
     
     
         8 . The controller of  claim 7 , wherein adjusting a chromaticity or luminance of the contributing color associated with the first component color subfield:
 obtaining tristimulus values for light used to illuminate the first component color;   computing a scaling factor based on the first and second aggregate weights;   adjusting the tristimulus values for the light used to illuminate the first component color using the scaling factor; and   identifying at least one light source intensity, for illuminating a second subframe associated with the first component color, based on the adjusted tristimulus values.   
     
     
         9 . The controller of  claim 4 , wherein the at least one display parameter includes a gamut mapping function applied to the second image data. 
     
     
         10 . The controller of  claim 9 , wherein adjusting the gamut mapping function includes:
 determining tristimulus coordinates of the second output white point based on the first and second aggregate weights;   obtaining tristimulus coordinates of a target output white point;   computing scaling factors based on the tristimulus coordinates of the second output white point and the tristimulus coordinates of the target output white point; and   transforming the second image data using a transformation formed based on the scaling factors.   
     
     
         11 . The controller of  claim 1  comprising a processor capable of processing image data, the processor being capable of communicating with a memory device and a display including a plurality of display elements. 
     
     
         12 . The controller of  claim 11  being further capable of sending at least a portion of the image data to a driver circuit, the driver circuit being capable of sending at least one signal to the display. 
     
     
         13 . The controller of  claim 11 , wherein the processor is capable of receiving the image data from an image source module and wherein the image source module includes at least one of a receiver, transceiver, and transmitter. 
     
     
         14 . The controller of  claim 13 , wherein the processor is capable of receiving input data from an input device. 
     
     
         15 . A non-transitory computer-readable medium comprising computer code instructions stored thereon, which when executed cause a processor to:
 receive first image data for a first image frame;   generate, for each of a plurality of component colors, a respective number of first subframes based on the first image data, wherein at least two component colors are associated with different respective numbers of first subframes, such that the generated first subframes are associated with a first output white point;   cause the generated first subframes to be displayed;   receive second image data for a second image frame;   determine, for each of the plurality of component colors, a respective number of second subframes, for at least one component color of the plurality of component colors, the respective number of second subframes is different than the respective number of first subframes for that component color;   generate the second subframes based on the second image data, such that a second output white point associated with the second image frame is substantially the same as the first output white point; and   cause the generated second subframes to be displayed.   
     
     
         16 . The computer-readable medium of  claim 15 , wherein for the generated second subframes, the plurality of component colors are associated with substantially equal respective duty cycles. 
     
     
         17 . The computer-readable medium of  claim 15 , wherein for the generated second subframes, the plurality of component colors are associated with substantially equal respective cumulative luminances. 
     
     
         18 . The computer-readable medium of  claim 15 , wherein generating the second subframes includes:
 determining a number of subframes and subframe weights for each of the component colors, such that a first aggregate weight associated with a first component color is different than a second aggregate weight associated with a second component color;   adjusting at least one display parameter used to output the second image frame based on the first and second aggregate weights, such that the second output white point is shifted towards the first output white point; and   generating the second subframes according to the identified numbers of subframes and the identified subframe weights.   
     
     
         19 . The computer-readable medium of  claim 18 , wherein the at least one display parameter includes a duty cycle of the first component color. 
     
     
         20 . The computer-readable medium of  claim 19 , wherein adjusting the duty cycle of the first component color includes:
 determining a cumulative duty cycle for the first component color based on the first aggregate weight;   determining a target cumulative duty cycle based on the first and second aggregate weights;   computing a scaling factor for the first component color based on the cumulative duty cycle for the first component color and the target cumulative duty cycle; and   determining display periods for second subframes associated with the first component color using the scaling factor.   
     
     
         21 . The computer-readable medium of  claim 18 , wherein the at least one display parameter includes at least a chromaticity or luminance of light used to illuminate the first component color. 
     
     
         22 . The computer-readable medium of  claim 18 , wherein the at least one display parameter includes a gamut mapping function applied to the second image data. 
     
     
         23 . A method for forming an image frame, comprising:
 receiving first image data for a first image frame;   generating, for each of a plurality of component colors, a respective number of first subframes based on the first image data, wherein at least two component colors are associated with different respective numbers of first subframes, such that the generated first subframes are associated with a first output white point;   causing the generated first subframes to be displayed;   receiving second image data for a second image frame;   determining, for each of the plurality of component colors, a respective number of second subframes, for at least one component color of the plurality of component colors, the respective number of second subframes is different than the respective number of first subframes for that component color;   generating the second subframes based on the second image data, such that a second output white point associated with the second image frame is substantially the same as the first output white point; and   causing the generated second subframes to be displayed.   
     
     
         24 . The method of  claim 23 , wherein for the generated second subframes, the plurality of component colors are associated with substantially equal respective duty cycles. 
     
     
         25 . The method of  claim 23 , wherein for the generated second subframes, the plurality of component colors are associated with substantially equal respective cumulative luminances. 
     
     
         26 . The method of  claim 23 , wherein generating the second subframes includes:
 determining a number of subframes and subframe weights for each of the component colors, such that a first aggregate weight associated with a first component color is different than a second aggregate weight associated with a second component color;   adjusting at least one display parameter used to output the second image frame based on the first and second aggregate weights, such that the second output white point is shifted towards the first output white point; and   generating the second subframes according to the identified numbers of subframes and the identified subframe weights.   
     
     
         27 . The method of  claim 26 , wherein the at least one display parameter includes a duty cycle of the first component color. 
     
     
         28 . The method of  claim 27 , wherein adjusting the duty cycle of the first component color includes:
 determining a cumulative duty cycle for the first component color based on the first aggregate weight;   determining a target cumulative duty cycle based on the first and second aggregate weights;   computing a scaling factor for the first component color based on the cumulative duty cycle for the first component color and the target cumulative duty cycle; and   determining display periods for second subframes associated with the first component color using the scaling factor.   
     
     
         29 . The method of  claim 26 , wherein the at least one display parameter includes at least a chromaticity or luminance of light used to illuminate the first component color. 
     
     
         30 . The method of  claim 26 , wherein the at least one display parameter includes a gamut mapping function applied to the second image data.